We are excited to announce our latest publication in Additive Manufacturing demonstrating a new Self-Terminating Etching Process (STEP) for titanium alloys. It if the first work exploiting sulfur-based corrosion and scale formation to improve Additive Manufacturing. Self-terminating etching process for automated support removal and surface finishing of additively manufactured Ti-6Al-4V.
Abstract: The advent of Additive Manufacturing (AM) has widened the design space for Ti-6Al-4 V (Ti64) components. However, the complex geometries fabricated using AM can result in high post-processing costs due to challenges associated with support removal, powder removal, and improving surface finish. To address these issues, this work introduces a novel, self-terminating etching process for Ti64 alloys that can remove support structures and trapped powder while also improving surface finish for both exterior and interior features. The component is first treated in a furnace to sulfidize the outer 50–150 µm of its surface and the supports. Next, this sulfide layer is selectively dissolved in a solution of 5 M H2SO4 and 0.25 M Na2MoO4. This solution readily dissolves sulfides without dissolving the Ti64 base metal and enables this etching process to be uniquely self-terminating at the sulfide/Ti64 interface. For this work, the amount of Ti64 converted to sulfides as a function of sulfidation temperature, the surface roughness before and after each sulfidation-dissolution cycle, and the microstructural evolution was quantified. The inherently self-terminating nature of this novel process means that, for the first time, post-processing of Ti64 components can be done in a geometry agnostic manner with the knowledge that a specified and known amount of material will be removed from all surfaces. As a result, support structures and trapped powder can be removed with ease at the same time that the surface finish is improved. This process is expected to reduce post-processing costs while expanding the design space for additively manufactured Ti64 parts.